An intake duct for an internal combustion engine includes a tubular wall configuring an intake passage. The wall includes segments that are separate from each other in a circumferential direction of the wall. At least one of the segments is made of a compression-molded fibrous body. Each of the segments includes a flange protruding radially outwards from the wall and having a joint. The joint of the flange of each of the segments and the joint of the flange of the corresponding one of the segments are joined to each other. Each of the flanges includes an opposing surface opposed to the corresponding one of the flanges. The opposing surface is provided with a step portion that is located closer to a proximal side of the flange than to the joint and forms a step in a thickness direction of the flange.